Merge pull request #1953 from ahopper/fix-make-MONITORINFO-a-struct

Fix make monitorinfo a struct

src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs

@@ -987,7 +987,7 @@ namespace Avalonia.Win32.Interop
         
         [DllImport("user32", EntryPoint = "GetMonitorInfoW", ExactSpelling = true, CharSet = CharSet.Unicode)]
         [return: MarshalAs(UnmanagedType.Bool)]
-        public static extern bool GetMonitorInfo([In] IntPtr hMonitor, [Out] MONITORINFO lpmi);
+        public static extern bool GetMonitorInfo([In] IntPtr hMonitor, ref MONITORINFO lpmi);
 
         [return: MarshalAs(UnmanagedType.Bool)]
         [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Unicode, EntryPoint = "PostMessageW")]
@@ -1055,12 +1055,17 @@ namespace Avalonia.Win32.Interop
         }
 
         [StructLayout(LayoutKind.Sequential)]
-        internal class MONITORINFO
+        internal struct MONITORINFO
         {
-            public int cbSize = Marshal.SizeOf<MONITORINFO>();
+            public int cbSize;
-            public RECT rcMonitor = new RECT();
+            public RECT rcMonitor;
-            public RECT rcWork = new RECT();
+            public RECT rcWork;
-            public int dwFlags = 0;
+            public int dwFlags;
+
+            public static MONITORINFO Create()
+            {
+                return new MONITORINFO() { cbSize = Marshal.SizeOf<MONITORINFO>() };
+            }
 
             public enum MonitorOptions : uint
             {

src/Windows/Avalonia.Win32/ScreenImpl.cs

@@ -26,8 +26,8 @@ namespace Avalonia.Win32
                     EnumDisplayMonitors(IntPtr.Zero, IntPtr.Zero,
                         (IntPtr monitor, IntPtr hdcMonitor, ref Rect lprcMonitor, IntPtr data) =>
                         {
-                            MONITORINFO monitorInfo = new MONITORINFO();
+                            MONITORINFO monitorInfo = MONITORINFO.Create();
-                            if (GetMonitorInfo(monitor, monitorInfo))
+                            if (GetMonitorInfo(monitor,ref monitorInfo))
                             {
                                 RECT bounds = monitorInfo.rcMonitor;
                                 RECT workingArea = monitorInfo.rcWork;

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -837,9 +837,9 @@ namespace Avalonia.Win32
 
             if (monitor != IntPtr.Zero)
             {
-                MONITORINFO monitorInfo = new MONITORINFO();
+                MONITORINFO monitorInfo = MONITORINFO.Create();
 
-                if (GetMonitorInfo(monitor, monitorInfo))
+                if (GetMonitorInfo(monitor,ref monitorInfo))
                 {
                     RECT rcMonitorArea = monitorInfo.rcMonitor;